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Full text of "The manufacture and properties of iron and steel"

THE BLAST FUKNACE.
75
cent, of free hydrogen, and 0.3 per cent, of free oxygen, the hydrogen coming partly from the volatile matters of the coke and partly from the decomposition of moisture in the atmosphere. In a humid summer day this moisture alone would be sufficient to* give 1.5 per cent, of hydrogen in the gas.
The results found by calculation agree closely with the analyses of actual gases, as shown by the following averages of gas samples, each sample being collected throughout the space of one hour or more. In each case a comparison is made between the actual figures and the line in the foregoing table where the carbon ratio and the working conditions are about the same. The figures given for a carbon ratio of 1.34 are taken from Gayley's paper on dry blast; the other analyses are all from Steelton furnaces.
	Ratio.	CO.,	CO	N+O+H
Actual 5 tests                         . . . •	2.97	9.9	29.5	60.6
Table ..............         ......	3.00	9.8	29.3	60.9
Actual 4 tests                             . .	2.19	12.1	26.6	61.4
Table    ........                .....	2.20	12,0	26.4	61.6
Actual 2 tests ..................	1.71	13.6	23.3	63.2
Table                                      ....	1.70	13.8	23.5	62.7
Actual.. ...        ...             ......	1.24	16.0	19.9	64.1
Table	1.25	16.9	21.2	61.9
				
The table shows that a, wasteful furnace using high fuel and having a high carbon ratio requires more air per ton of iron and delivers more gas, but uses about the same air and delivers about the same volume of gas per ton of coke burned. An increase in the amount of limestone increases in slight degree the volume of gas, but the quality of the gas depends altogether upon how much of the carbonic acid is converted into carbonic oxide. It is shown also that it is of little moment, as far as the gas is concerned, whether or not the stone contains magnesia. An increase or decrease in the amount of moisture in the air has little influence upon the amount or composition of the gas so far as theoretical calculation is concerned, but this has no relation to the well-known fact that with dry air less fuel is needed and a better carbon ratio obtained.
SBC. IIo.—Rough estimation of the volume of the gas.—The volume of gas can be roughly calculated by simple means. The air entering the tuyeres contains 79 per cent, of nitrogen by volume, while the tunnel head gas carries about 60 per cent. The specific gravity of the gas is almost exactly the same as that of air, and as